<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			.aaa{
				width: 0;
				height: 0;
				
			    border-width: 20px;
			    border-style: dashed dashed solid;
			    border-color: transparent transparent red;
			    
			}
			
			
			
			.bbb{
				width: 0;
				height: 0;
				
			    border-width: 20px;
			    border-style: dashed dashed solid;
			    border-color: red transparent transparent;
			}
			.ccc{
				width: 0;
				height: 0;
				
			    border-width: 20px;
			    border-style: dashed dashed solid;
			    border-color: transparent red transparent transparent;
			}
			.ddd{
				width: 0;
				height: 0;
				
			    border-width: 20px;
			    border-style: dashed dashed solid;
			    border-color: transparent transparent transparent red;
			}
		</style>
	</head>
	<body>
		<p>将宽度设置为0，只设置边框宽度，然后去掉要去掉的部分</p>
		<div class="aaa" onclick="aaa()"></div>		<br /><hr />
		<div class="bbb"></div>		<br /><hr />
		<div class="ccc"></div>		<br /><hr />
		<div class="ddd"></div>
		
		
		
	</body>
</html>
<script type="text/javascript">
	function aaa(){
		console.log(1)
	}
</script>